Currently, the common packaging approach is to flip or turn over the substrate mounted with the chip for packing up the light emitting chip as the inner projection light source of the circuit board. As the chip mounted substrate and the circuit board are usually connected through the ball grid array (BGA), numerous factors such as the height of the solder ball and the melting degree during the reflow process have to be well controlled. However, owing to the uncertainty, it is difficult to upgrade the alignment accuracy and the precision and reproducibility of the horizontal level of chip mounted substrate may be distressed, as well as the coupling accuracy of the laser light source and the optical waveguide within the circuit board.
Another approach of the light emitting chip package is to project the light into the circuit board through the substrate via(s) and the light emitting chip is guided through the via and emits the light to the optical waveguide However, as the distance is quite far away, high-performance lens is required to assist alignment.
The industry has a great demand in developing the packaging technology to pack the light emitting/receiving chip(s) into the circuit board.